With the development of sophisticated electronic components, including those capable of increasing processing speeds and higher frequencies, having smaller size and more complicated power requirements, relatively high internal temperatures can be generated within the electronic components themselves. These high internal temperatures may become more exacerbated as microprocessors, integrated circuits, and other small feature electrical components and systems are integrated into or placed alongside other devices.
Most microprocessors, integrated circuits and other sophisticated electronic components typically operate efficiently only under a certain range of threshold temperatures. Much of the range of threshold temperatures is exhausted by the internal temperature of the electrical components and the radiant temperature of other surrounding electronics. Many modern electronic circuits begin to exhibit problems at external temperatures between about 80 and 100 degrees C., and begin to fail at temperatures barely above 100 degrees C. Consequently, additional environmental temperature conditions acting upon the electrical components can raise the temperature of the components above their operation thresholds, which unfortunately limits using electronic circuitry in many desirable, but harsh environmental condition locations.
Excessive heat generated or applied during operation of these components can not only harm their own performance, but can also degrade the performance and reliability to the point of failure of overall systems that include such components. The increasingly wide range of environmental conditions, including temperature extremes, in which electronic systems are expected to operate, intensifies these negative effects. For instance, when the temperatures of the electronic components rise above the operational-threshold temperatures for even a short time, junctions of silicon devices can fail, solder pads can reflow thereby causing undesirable cold solder joints, thermistors and other temperature sensing components can shift thereby causing the electronics to become inoperable, printed circuit boards and the materials thereof can become malleable and be easily damaged, and other electromechanical failures can occur.
With the increased need for using microelectronic devices under harsh environmental conditions, thermal management becomes an increasingly important element of the design of electronic products. As noted, both performance reliability and life expectancy of electronic equipment are inversely related to the component temperature of the equipment. For instance, a reduction in the operating temperature of a device such as a typical silicon semiconductor can correspond to an exponential increase in the reliability and life expectancy of the device. Therefore, to maximize the life-span and reliability of a component, controlling the device operating temperature within the limits set by the designers is of vital importance.
Many legacy devices and systems use heat sinks to combat the detrimental effects of internal heat dissipation and externally applied heat. Heat sinks are components that facilitate heat dissipation from the surface of a heat source, such as a heat-generating electronic component, to a cooler environment, usually air. The primary purpose of a heat sink is to help maintain the device temperature below the maximum allowable temperature specified by its designer and/or manufacturer.
Limitations exist, however, with the use of heat sinks. First, heat sinks can become large, as heat sinks seek to increase the heat transfer efficiency between the components and the ambient air by primarily increasing the surface area that is in direct contact with the air. In many applications, heat sinks are formed with fins or other structures to increase the surface area of the heat sink to effect heat dissipation from the electronic component through the heat sink and then to the air. The size constraints of the heat sinks and other associated electronic circuitry greatly limit reduction of electronic packaging and thereby hinder placing electronic circuitry in small locations.
Second, due to inefficient heat-sink-to-air heat transfer, damage to the underlying electronic circuitry can occur before the heat sink can react. Furthermore, the heat sink may actually transfer heat into an operating circuit when the external temperature is much greater than the internal heat of the underling circuitry. And as the external temperature is applied to such heat sinks, the heat transfer to the circuitry may be delayed due to the thermal conductivity of the heat sink. Thus, any potential advantages of external temperature sensors used to protect the underlying circuitry may be thwarted.
What is therefore needed is an apparatus and method for protecting and preserving an electronic device or assembly from short-term exposure to a destructive high temperature environment that does not deleteriously constrain size, weight, cost, serviceability and reliability of the electronic components therein.